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H. Shao, Y. Ke, P. Zhang, H.J. Kaplan, D. Sun; Retinal Pigment Epithelial (RPE) Can Either Promote or Inhibit the in vitro Activation of IRBP–Specific T Cells Depending on the Activation Status of the T Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5142.
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In previous studies we have shown that RPE are able to express MHC antigen in vitro if they were exposed to inflammatory cytokines such as IFN–γ. Current study determines the role of RPE in the activation of uveitogenic CD4 and CD8 T cells in the inflamed eye.
RPE cells were isolated from 10 day–old Lewis rats and used for experiments after two or three in vitro passages. Uveitogenic T cell cells were isolated from the uveitogenic IRBP peptide (IRBP1177–1191 or R16) immunized Lewis rats and labeled with CFSE (Carboxy–Fluorescein Diacetate, Succinimidyl Ester) before subjecting to an in vitro stimulation with R16 and APCs in the absence or presence of RPE. Two days later, T cells were separated on a Ficoll gradient, cultured in various concentrations of IL–2–containing medium for another 3–4 days, stained with PE–conjugated anti–rat CD4 or CD8 antibodies and analyzed by FACS analysis.
When T cells were stimulated with high concentrations of immunizing peptide, RPE cells reduced CD4 activation but enhanced CD8 activation. However, when T cells were stimulated with low concentration of immunizing peptide, RPE cells increased CD4 but decreased CD8 T cell expansion. In addition, in vivo primed IRBP–specific T cells, but not the native syngeneic T cells, can be directly activated by the undefined factors in the cultured RPE supernatants.
RPE cells can either promote or inhibit the activation of invading autoreactive T cells, depending on the activation status of the responder T cell. In addition, CD4 and CD8 autoreactive T cells differ in their susceptibility to the promoting or inhibitory effect of the RPE.
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